1. Field of the Invention
The present invention relates to an elasticized unit, apparatus for making such units, garments incorporating the units, and methods for making such garments. Herein the elasticized unit means a unit containing a plurality of elastic strands providing a sealed tight fit so as to avoid the leakage of body excrement.
2. Description of the Prior Art
In underwear, especially baby's diapers and female napkin, elasticity is essential for providing a sealed tight fit between the skin and the fabric. For securing the elasticity elastic strings are used around the leg or waist area of the wear, and the wearer fastens the string after he puts it on. Alternatively, when the wearer puts it on, the strings naturally tighten the skin. The strings are fixed to the garment in stitches or by melting or bonding. The fixing work is labor- and time-consuming, thereby leading to a high production cost.
To save cost the stitching method is generally avoided and the melting or bonding (with an adhesive) method is commonly adopted. Under the known methods a problem is that the fabric of the garment and the elastic material, such as strings, have different elasticity. In fixing elastic strings, the base material of the garment is stretched to its own full extent, and allowed to contract after the strings are fixed. However it is difficult to fix the elastic strings to the stretched fabric. To overcome the difficulty, experience and skill is required.
To facilitate the fixing work many proposals have been made but they are not satisfactory in efficiency and cost.
To explain the background of the present invention reference will be made to FIG. 3, which is a perspective view showing a known disposable diaper, partly broken to show the internal structure. The diaper 1 is made up of a permeable nonwoven sheet 2 and a sealing sheet (e.g. a plastic film) 3 overlaid with an absorbent sheet 4 having a smaller area than the sheets 2 and 3. The sheets 2 and 3 are thermally jointed to each other at their peripheries C. The reference numeral 10 denotes an elastic string provided in its stretched state along the opposite side margins of the sealing sheet 3.
The diaper shown in FIG. 3 is produced in the manner shown in FIG. 4:
The permeable sheet 2 is supplied onto the absorbent sheet 4 from a first roll 8, and the sealing sheet 3 is supplied to the under-surface of the absorbent sheet 4 from a second roll 9. These sheets 3 and 4 are pressed and laminated at 22 by a pair of rollers 14, 19. The reference numerals 15 and 16 denote nozzles through which an adhesive is preliminarily coated on the sheets 2 and 3. An elastic strand 10 is supplied from rollers 11, and adhered to the sheet 3 in its stretched state. The laminated sheet is appropriately trimmed, and finally cut to desired lengths at 17. In this way a disposable diaper shown in FIG. 3 is produced. The reference numeral 13 denotes a heater whereby the elastic strand is thermally cut.
In using this diaper the permeable sheet 2, especially a narrow portion (N), is kept in contact with the baby's crotch, and a wide portion (W) is kept in contact with his belly and back. The corners 5 and 5a, 6 and 6a of the diaper 1 are releasably fixed to each other by adhesive tapes.
In this way the sealed tight fit between the cloth and the skin of the baby is secured. In the method mentioned above the elastic strands 10 are arranged in the direction in which the sealing sheet 3 runs, thereby keeping the strands in their stretched state while the sheet 3 is running. This may be advantageous but when it is cut it often happens that the adhesive in the part 10a near the cut still remains too fluid to fix to the sheet. This part tends to become separated from the sheet during use. To avoid this problem a special kind of adhesive is used or the amount of the adhesive is increased. Nevertheless the bond between the sheet and the elastic strands becomes poor.
The leakage of body excretion also occurs through the waist area of the diaper, so that it is required for the cloth to fit the baby's belly and back areas. Normally the diaper is made so as to tighten the fabric around them but that part which keeps contact with the skin tends to become loose over a period of use, thereby causing a gap between the skin and the cloth. The loose diaper often occurs as a result of babies' action. The disposable diapers have the difficulties pointed out above, that is, one difficulty in the production, and the other in the maintenance of the sealed tight fit for the skin.